Conventionally, so-called compact disks (hereinafter referred to as CDs) have been widely used whereon successive information such as music information is recorded as digital signals in the form of optically detectable minute pits. Meanwhile, CD-ROMs (Compact Disc Read Only Memory), whereon discrete information such as computer-use data as well as music information is recorded, have been viewed with interest for its characteristics of large storage capacity and high productivity and already come into use (hereinafter CD-ROMs are included in CDs for convenience). Information on the CDs is reproducible through optical disk reproducing devices for only reproduction (CD players or CD-ROM drives).
FIG. 11 and FIG. 12 are schematic views illustrating a signal format used in the CDs. As shown in FIG. 11, a frame 50a of a recording signal is composed of a frame synchronizing signal 50b indicating a head of the frame, a sub-code 50c for additional information data, and a data field 50d having 24-byte main information data and 8-byte error detection and correction parity code added thereto.
In addition, the data field 50d is formed by an error detecting and correcting method including non-complete interleaving called CIRC (Cross Interleaved Reed Solomon Code).
As shown in FIG. 12, ninety-eight of the frame 50a form a sub-coding frame 51a (hereinafter referred to as a sector). Further, ninety-eight of the sub-code 50c in each frame 50a form a sub-coding block 51c. Information such as track numbers (corresponding to music numbers when main information is of music programs), and absolute address information on the disk are indicated by data in the sub-coding block 51c.
Since the length of each sector corresponds to 13.3 [ms], seventy five sectors are equivalent to a second. In this case, sector numbers on the disk can be described based on the following data, "minute": "second": "a sector number in one second (taking a value from 00 through 74)". The sector number corresponds to successive time-indicating information and position-indicating information and consecutively increases from an innermost portion to an outermost portion of the disk.
The frame synchronizing signal 51b and the data field 51d are respectively composed of ninety-eight frames of the frame synchronizing signal 50b and ninety-eight frames of data field 50d.
FIG. 10 is a typical depiction illustrating an area allocation on the CD or the CD-ROM. A disk 52 is provided with a main information recording area 52b and a TOC (Table of Contents) area 52a. The main information recording area 52b stores main information such as music information and sector numbers of the sub-code 50c. On the other hand, the TOC area 52a stores additional information related to each piece of main information recorded in the main information recording area 52b, such as a track number and a recording start sector number of each track recorded by using the sub-code 50c. In the TOC area 52a, other kinds of additional information are also recorded by using the sub-code 50c such as control information for determining whether information recorded on a track is audio information such as music information or computer-use data.
According to the format, when loading the disk 52 into the CD player or CD-ROM drive, information defined by the sub-code 50c in the TOC area 52a is reproduced, then the number of main information (corresponding to the number of music programs for music information), sector numbers of recording start positions of respective information and a sort of information (whether successive information such as audio information or discrete information such as computer-use data) are recognized. Thereafter, an access operation to a desired track is promptly carried out upon receiving instructions to perform a reproducing operation by collating information in the TOC area 52a with sector numbers of the sub-code 50c in the main information recording area 52b.
When recording on the CDs or CD-ROM drives, a so-called CLV (Constant Linear Velocity) system is employed for a rotation control. With this system, a recording density becomes constant at any position of the disk. This characteristic is preferable for increasing a recording capacity. In the CD players or the CD-ROM drives, the CLV control is carried out by controlling a disk rotation such that an interval of the reproduced signal, for example, the frame synchronizing signal, which is recorded on the CD or CD-ROM at CLV, becomes a reference length.
When using a re-writable disk such as a magneto-optical disk which has been recently developed, whereon various types of information such as music information, computer-use data, etc., are recorded, the information recording and reproducing apparatus is preferably designed to be compatible with the conventional CD player by employing a common reproducing method.
In this case, especially for a disk whereon information has not been recorded (hereinafter referred to as a blank disk), an access operation to sector positions prior to recording nor the CLV control required during the recording operation cannot be carried out. This is because the blank disk does not store absolute address information defined by the sub-code of the signal format used in the CDs or CD-ROMs nor the frame synchronizing signal used in the CLV control.
To counteract the above-mentioned problems, the following method is proposed as an alternative method for recording absolute addresses without using the sub-code information. In this method, guiding grooves on the disk are deviated inward or outward in a radial direction, or the widths of the guiding grooves on the disk are varied depending on the value of each bit: "0" or "1" after being "biphase-mark" modulated (for example, see U.S. Pat. No. 4,907,216).
In this case, if a frequency band of a "biphase-mark" modulated absolute addresses and a frequency band of "EFM" (Eight to Fourteen Modulation) modulated recording information are set to differ, the respective reproducing operations can be performed separately. This enables access to an area even whereon no information has been recorded by using the absolute addresses associated with the guiding grooves.
Moreover, by using a reproduction carrier component of the absolute address, an accurate CLV control can be attained. This is also true during the recording operation.
The control information such as position-indicating information related to each piece of main information recorded using the discussed method is recorded by the sub-code in response to the absolute address information stored in a predetermined area of the disk, i.e., a TOC area. With this arrangement, upon loading the disk, the sub-code information stored in the TOC area is reproduced. As a result, the control information related to each piece of main information is recognized, thereby promptly carrying out a reproducing operation from a desired track according to the instructions for reproduction as in the case of the conventional CD players.
As to the recording operation, whether or not the main information has been recorded is determined by using the control information, thereby performing a follow-up recording or rewriting operation. The control information also serves for protecting the recorded information.
The discussed recording medium whereon a user can record information is a blank disk storing only pre-recorded address information, etc., when the user obtains the disk from a manufacturer.
In the information recording and reproducing apparatus, when loading the re-writable disk, first, a reproducing operation is carried out from the TOC area. Next, it is determined whether or not the disk stores information to be reproduced, or whether or not there still have a recordable area in the main information recording area. Here, when the loaded disk is determined to be a blank disk, it is determined that the reproducing operation cannot be performed from the disk, since the disk does not store any pieces of control information in the TOC area. In such a case, the disk is considered as a blank disk. This means that the entire main information recording area is recognized as a recordable empty area.
However, in adopting the discussed method, the following problems may arise. In the case where a reproducing function is damaged of the information recording and reproducing apparatus, even if useful main information and the control information related to each piece of main information have been recorded on the disk, it would be determined that the reproducing operation of the control information cannot be performed from the TOC area. In such a case, the recorded main information cannot be reproduced. Moreover, additional pieces of main information may be recorded since the entire area is recognized as an empty area, thereby presenting a possibility of destroying the useful main information and the control information which have been already recorded.
The discussed information recording and reproducing apparatus employing the portable recording medium is usually arranged such that the recording operation of the information is performed within a predetermined range of a signal quality. This enables the information recording and reproducing apparatus to be compatible with other information recording and reproducing apparatuses. However, in practice, the problem may arise in that the information recorded on the disk with an information recording and reproducing apparatus A can be reproduced with the information recording and reproducing apparatus A but with an information recording and reproducing apparatus B due to the differences in their performances including a degree of deterioration or the differences in adaptability to the recording medium.
In this case also, when using the information recording and reproducing apparatus B, the reproducing operation of the control information cannot be performed from the disk whereon information is recorded using the information recording and reproducing apparatus A. In both cases, since the disk is considered as a blank disk, the reproducing operation of the recorded main information cannot be performed. Moreover, there is a possibility of destroying the useful main information and the control information which have been previously recorded.
In order to counteract this, for example, another method has been proposed wherein the reproducing operation of the information is performed a plurality of times under a constant condition or under different conditions. However, with this method, upon loading a disk, it takes a long time to determine whether or not the disk is a blank disk.